Evaluation of intestinal mucosal function by measuring expired (14)CO(2) after oral administration of (14)C-putrescine

Moderate Dietary Protein Restriction Optimized Gut Microbiota and Mucosal Barrier in Growing Pig Model

Appropriate protein concentration is essential for animal at certain stage. This study evaluated the effects of different percentages of dietary protein restriction on intestinal health of growing pigs. Eighteen barrows were randomly assigned to a normal (18%), low (15%), and extremely low (12%) dietary protein concentration group for 30 days. Intestinal morphology and permeability, bacterial communities, expressions, and distributions of intestinal tight junction proteins, expressions of biomarkers of intestinal stem cells (ISCs) and chymous bacterial metabolites in ileum and colon were detected. The richness and diversity of bacterial community analysis with Chao and Shannon index were highest in the ileum of the 15% crude protein (CP) group. Ileal abundances of Streptococcaceae and Enterobacteriaceae decreased respectively, while beneficial Lactobacillaceae, Clostridiaceae_1, Actinomycetaceae, and Micrococcaceae increased their proportions with a protein reduction of 3 percentage points. Colonic abundances of Ruminococcaceae, Christensenellaceae, Clostridiaceae_1, Spirochaetaceae, and Bacterodales_S24-7_group declined respectively, while proportions of Lachnospiraceae, Prevotellaceae, and Veillonellaceae increased with dietary protein reduction. Concentrations of most bacterial metabolites decreased with decreasing dietary protein concentration. Ileal barrier function reflected by expressions of tight junction proteins (occludin, zo-3, claudin-3, and claudin-7) did not show significant decrease in the 15% CP group while sharply reduced in the 12% CP group compared to that in the 18% CP group. And in the 15% CP group, ileal distribution of claudin-3 mainly located in the cell membrane with complete morphological structure. In low-protein treatments, developments of intestinal villi and crypts were insufficient. The intestinal permeability reflected by serous lipopolysaccharide (LPS) kept stable in the 15% CP group while increased significantly in the 12% CP group. The expression of ISCs marked by Lgr5 slightly increased in ileum of the 15% CP group. Colonic expressions of tight junction proteins declined in extremely low protein levels. In conclusion, moderate protein restriction (15% CP) can optimize the ileal microbiota structure via strengthening beneficial microbial populations and suppressing harmful bacterial growth and altering the function of ileal tight junction proteins as well as epithelial cell proliferation.

Rapid absorption of luminal polyamines in a rat small intestine ex vivo model

BACKGROUND AND AIM

Not only biosynthesis, but also uptake from the intestinal lumen, are important polyamine sources. However, there has been no information regarding dynamic polyamine transport in the small intestine. We evaluated polyamine uptake from the small intestine using a rat ex vivo model.

METHODS

The organ block consisting of the small intestine and blood vessels was used. The isolated small intestine was placed in a warmed saline bath and perfused in a non-circulating manner via the superior mesenteric artery. Radio-labeled putrescine, spermidine or spermine (7.4 x 104 Bq), with 1.0 mL of phosphate buffer saline (pH 7.4) was instilled into the jejunal lumen for 1 min. Blood samples from the portal vein were collected and sample radioactivity was determined. In another experiment, an immunohistochemical study of polyamine was performed.

RESULTS

After 14C-polyamine instillation, radioactivity in the portal vein samples immediately increased and then decreased gradually. The absorptive pattern did not differ among the three polyamines. The recovery rates from radioactivity at the portal vein among the three polyamines were approximately 61-76% during the initial 10 min after the administration of 14C-polyamine, and were not different from each other. Aminoguanidine, which inhibits putrescine degradation, significantly suppressed initial putrescine uptake and recovery percentage. The intraluminal administration of spermine caused an increase in the immunoreactivity of the spermine antibody in the intestinal villi.

CONCLUSION

Luminal polyamines were rapidly absorbed by the intestinal mucosa and then subsequently transferred into the portal vein using a rat ex vivo model. The prior administration of aminoguanidine significantly inhibited initial putrescine transport into the portal vein.